Possible Expectancy Violations on Frontage Roads and Conventional Roads at Interchanges and Lane Assignment Traffic Control Device Solutions

摘要

The intersection and mandatory movement lane control signs placed on intersection approaches are critical to safe and efficient intersection operations. Ramp, frontage road, and cross-street approaches to interchangesoften widen at intersections to accommodate additional through or turn lanes. Currently, there is inconsistencyin conveying to drivers how they should align themselves upstream of a diamond intersection to maneuver fortheir desired turning movement as the intersection widens. These inconsistencies can result in drivers makingincorrect lane selection, which may result in late lane changes or illegal turns. This paper focuses on theexpectancy violations that were discovered by a driver survey portion of a larger project which includedpractitioner surveys and a field evaluation of sign alternatives. The driver survey sampled 204 Texas drivers infour cities in a computer-based survey. The questions reported here focused on driver expectations of lanemovement and assignment on frontage road approaches to cross streets on freeway on and off ramps. Findingsshowed that drivers are often incorrect in their assumptions about lane assignment when approachingintersections, which indicates a greater need for advanced lane control signs. A new sign design, adopted fromAustralian practice, which graphically shows lane additions and drops, was the most effective for cases wherethe downstream geometry varied from driver expectations.